The ankle joint is very stable and resistant to injury. However, since it is one of the most used and abused joints, it is nonetheless frequently injured, particularly upon participation in certain rugged sports, such as basketball and football. The ankle joint is the complex articulation joint of the fibula and tibia with the ankle bone or talus and the tarsal bones. The outer ankle knob or lateral malleolus is at the lower end of the fibula. The inner ankle knob or medial malleolus is at the lower end of the tibia. These are held tightly together by the tibiofibular ligaments to form the top half of the ankle joint or the receptacle known as a mortice which is occupied by the talus. The talus is held in the mortice by more ligaments. The inside ligament system comprises the deltoid ligament. The outside ligament system is more complex. The front ligament that goes forward from the lateral malleolus is called the anterior talofibular ligament. This ligament runs from the lateral malleolus to the ankle bone. A second ligament goes from the tip of the lateral malleolus straight down to the heel bone. This is called the calcaneofibular ligament. A third ligament, the posterior taleofibular ligament, runs directly back from the lateral malleolus to the ankle bone.
The most common injury in sports is an ankle sprain. This results when the ankle bone is forced or pried out of the mortice or ankle joint. It generally happens when the ankle is forceably rotated inward. A mild sprain occurs upon momentary displacement of the ankle bone and causes only mild stretching of the ligaments on the distal ankle. Severe strains involve tearing of ligaments upon dislocation of the ankle bone. When the ankle is forceably tipped inward, the first ligament to restrain this motion and, accordingly, the first to be injured is the anterior talofibular ligament. The next ligament to be injured, the calcaneofibular ligament, is seldom injured above, as usually the anterior talofibular ligament is injured first. Accordingly, it is important in the prevention of a sprain injury, or in preventing the aggravation of preexistent sprain injury, to protect first the anterior talofibular ligament and provide secondary protection for the calcaneofibular ligament. Various forms of gear are available to generally support and protect the ankle and deter it from movement in unintended direction. These include tape, elastic wrap and ankle braces of various types. However, such devices do not provide specific support to guard against injury to the anterior talofibular ligament and the calcaneofibular ligament.